1. Field
This document relates to a touch screen panel for a display device, and more particularly, to a touch screen panel for a display device capable of improving touch sensitivity.
2. Related Art
Various input devices, such as a keyboard, a mouse, a trackball, a joystick, a digitizer, and the like, are used to configure an interface between a user and home appliances or various information communication devices. However, the user has to learn how to use the input devices and the input device occupies a separate space, thus making it difficult to easily handle the products. Thus, a demand for simple and convenient input devices capable of reducing malfunction has been increasing day by day. A touch screen panel, through which the user inputs information by directly contacting the screen with his or her finger or a pen, was proposed to fulfil the demand.
The touch screen panel is applied to various display devices because it is simple and less malfunctioning, allows the user to input information without using an additional input device, and enables the user to perform quick and easy operations through content displayed on the screen.
Touch screen panels can be classified into a resistive type touch screen panel, a capacitive type touch screen panel, and an electromagnetic type touch screen panel based on a method for sensing a touched portion of the touch screen panel. The resistive type touch screen panel senses the touched portion by a voltage gradient depending on resistance in a state where a DC voltage is applied to a metal electrode formed on an upper substrate or a lower substrate. The capacitive type touch screen panel senses the touched portion by forming an equipotential surface on a conductive layer and sensing a voltage change location of upper and lower substrates based on a touch operation. The electromagnetic type touch screen panel senses the touched portion by reading an LC value induced by touching a conductive layer with an electronic pen. Also, optical type and ultrasonic type touch screen panels are known.
In the resistive type touch screen panel, if a user touches an upper substrate of the touch screen panel, a transparent conductive film of the upper substrate comes into mechanical contact with a transparent conductive film of a lower substrate of the touch screen panel. The touch screen panel detects a touched position by sensing an electric potential along an x-axis and an electrical potential along a y-axis generated when the transparent conductive films are contacted with each other. In a resistive type touch screen panel, a more exact touch position can be sensed because the touch position is determined by a mechanical contact. However, an analog digital converter (ADC) is needed because the touch position is indirectly determined by electrical potentials at x and y axes where the touch is performed. Furthermore, it is difficult to sense the touch position if the user touches the touch screen panel lightly.
On the other hand, the capacitive type touch screen panel has a matrix in which first electrode patterns arranged in an x-axis direction crossing second electrode patterns arranged in a y-axis direction. In the capacitive type touch screen panel, if the user touches an arbitrary position on the matrix, the touched position is detected by finding X and Y coordinates on the matrix where an electrostatic capacitance change occurs. Thus, an exact touch position can be detected even if the user touches the touch screen panel lightly.
Hereinafter, a related art capacitive type touch screen panel for a display device will be described with reference to FIGS. 1 and 2.
FIG. 1 is a top plan view showing a related art capacitive type touch screen panel for a display device. FIG. 2 is a cross-sectional view taken along line I-I′ of FIG. 1.
Referring to FIGS. 1 and 2, the touch screen panel includes a touch area A where a touch occurs, a routing wire area B, and a pad area C.
The touch area A includes a plurality of first touch electrode strings Tx arranged in parallel in a first direction (e.g., x-axis direction) on a substrate 10 and a plurality of second touch electrode strings Rx formed in parallel in a second direction (e.g., y-axis direction) so as to cross the strings of first touch electrodes Tx, with an insulation film interposed therebetween.
The routing wire area B includes a plurality of first routing wires RW1 formed on the outer periphery of the touch area A having the first and second touch electrode strings Tx and Rx, and respectively connected to the first touch electrode strings Tx. The routing wire area B also includes a plurality of second routing wires RW2 formed on the outer periphery of the touch area A having the first and second touch electrode strings Tx and Rx, and respectively connected to the second touch electrode strings Rx.
The pad area C includes a plurality of first routing pads TP respectively connected to the plurality of first routing wires RW1 and a plurality of second routing pads RP respectively connected to the plurality of second routing wires RW2.
In the touch screen panel shown in FIGS. 1 and 2, the first routing wires RW1 and second routing wires RW2 of the routing wire area B are disposed to be adjacent to each other, and therefore a parasitic capacitance is formed between the first and second routing wires RW1 and RW2. The first routing wires RW1 are respectively connected to the first touch electrode strings Tx functioning as a plurality driving electrode strings, and the second routing wires RW2 are respectively connected to the second touch electrode strings Rx functioning as a plurality of sensing electrode strings. Thus, the parasitic capacitance between them increases the noise of the touch screen panel, thus degrading touch performance.
Although the distance between the first routing wires and the second routing wires can be increased to reduce the size of the parasitic capacitance, the effect of this method is not great, and bezel size is increased, thus leading to another problem of a smaller touch area.